This invention relates in general to remote controlled switching of an electric load and more particularly concerns novel apparatus and techniques for disconnecting a load from operative connection with a power circuit in response to a remotely or locally generated disconnect control signal, and reconnecting the load to the power circuit either after a particular time delay or in response to a connect control signal.
The apparatus of the invention may be used by a plurality of remote stations to switch their respective loads into and out of connection with a power distribution circuit in response to control signals generated by a remote central control station. The apparatus of the invention will operate to reduce load disconnect transients in the power circuit by responding to staggered load disconnect signals to vary the time of disconnection of the various system loads and will reduce load connect transients by varying the automatic reconnect time delays of the various stations.
During particularly hot or cold days of the year, electric utilities typically operate at or near their maximum generating capacity since more generating capacity is required to serve the increased consumer load. However, instead of installing new generating capacity to meet peak consumer loads, some of the nonessential or interruptable load could be temporarily disconnected from the power system to reduce the power generating requirement of the system. Thus, electric loads such as water heaters, air conditioners, pool heaters and pumps, water and irrigation pumps, and space heaters could be temporarily disconnected from the power mains without undue discomfort, damage or economic loss to the user of the load.
Such a load switching function could be locally performed if the user would disconnect the load by simply switching the equipment off-line. However, a vast amount of presently installed equipment either does not have readily accessible switching gear or does not have a person available at all times to operate such gear. In addition, the user may not wish to turn off the load.
Therefore, it may be desirable for the electric utility to exercise control over such equipment so they can keep the load within the bounds of their generating capacity or share the burden of load disconnection among all classes of customers. This system control could be accomplished by combining the apparatus of the invention with the system disclosed in a prior patent to Jagoda et al, U.S. Pat. No. 4,012,734, which is assigned to the assignee of the present invention.
In addition, it is noted that a remote load switching apparatus could be used to switch a load in response to local control, for example a home computer, to automatically and more efficiently regulate the periods of energization of electrical appliances.
Accordingly, it is an important object of this invention to provide improved methods and means for disconnecting a load from electrical service.
It is another object of the invention to achieve the preceding object in response to a remotely generated signal.
It is still a further object of the invention to achieve one or more of the preceding objects while automatically reconnecting the load some preset time later.
It is still a further object of the invention to achieve one or more of the preceding objects while avoiding large transients on the electric system that might cause instability.
It is still a further object of the invention to achieve one or more of the preceding objects with a capability of reconnecting the load in response to a remotely generated signal.
It is still a further object of the invention to achieve one or more of the preceding objects with apparatus that is highly reliable, relatively inexpensive to produce and relatively immune to damage or false operation caused by induced or power line noise at various remote terminals.
These and other objects of the invention will become apparent from a review of the detailed specification which follows and a consideration of the accompanying drawings.